The present invention relates to a nuclear magnetic resonance apparatus which measures the nuclear magnetic resonance (will he termed "NMR" hereinafter) signals from hydrogen, phosphor, etc. in an object under test thereby to image the density distribution, relaxation time distribution, and the like of the nuclei.
Conventional NMR apparatus intended for the inspection and imaging of objects (e.g., human body) use various wrap coils specialized for the regions of interest, e.g., head and abdomen, and surface coils which are less affected by the movement of organ such as the heart. The surface coil has a higher sensitivity as compared with the head coil and abdomen coil, but it suffers from a limited view field, and therefore imaging of such a large section as the spine is carried out dividedly by shifting the position of the surface coil, resulting in a significant time consumption.
This problem is counterplotted by a method of virtually expanding the view field, as described in U.S. Pat. No. 4,825,162, in which a plurality of surface coils are arranged, with adjoining coils overlapping properly so that they do not couple, and the NMR signals received by the surface coils are hybridized. Although the arrangement of multiple surface coils overcomes the prior art deficiency of a narrow measuring view field, the advantage of the surface coil, i.e., high signal-to-noise (s/n) ratio, will be lost if the coil outputs are simply hybridized. A magnetic resonance apparatus described in U.S. Pat. No. 4,943,775 and another one described in publication "Magnetic Resonance in Medicine", Vol. 16, pp.192-225 published in 1990 are intended to achieve a wide view field as the whole and a high s/n ratio by rendering the quadrature phase detection and A/D conversion for the individual coil outputs before the signals are hybridized.